Re: [PATCH 4/5] hv: kvp: use wrappers to propaigate state

[Greg KH <gregkh@linuxfoundation.org>]

On Tue, Sep 15, 2015 at 05:37:53PM -0700, K. Y. Srinivasan wrote:
> From: Olaf Hering <olaf@aepfle.de>
> 
> The "state" is used by several threads of execution.
> Propagate the state to make changes visible. Also propagate context
> change in kvp_on_msg.
> 
> Signed-off-by: Olaf Hering <olaf@aepfle.de>
> Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
> ---
>  drivers/hv/hv_kvp.c |   39 +++++++++++++++++++++------------------
>  1 files changed, 21 insertions(+), 18 deletions(-)
> 
> diff --git a/drivers/hv/hv_kvp.c b/drivers/hv/hv_kvp.c
> index 74c38a9..778d353 100644
> --- a/drivers/hv/hv_kvp.c
> +++ b/drivers/hv/hv_kvp.c
> @@ -61,7 +61,7 @@
>   */
>  
>  static struct {
> -	int state;   /* hvutil_device_state */
> +	enum hvutil_device_state state;
>  	int recv_len; /* number of bytes received. */
>  	struct hv_kvp_msg  *kvp_msg; /* current message */
>  	struct vmbus_channel *recv_channel; /* chn we got the request */
> @@ -74,6 +74,9 @@ static struct {
>   */
>  static int dm_reg_value;
>  
> +#define kvp_get_state() hvutil_device_get_state(&kvp_transaction.state)
> +#define kvp_set_state(s) hvutil_device_set_state(&kvp_transaction.state, s)
> +
>  static void kvp_send_key(struct work_struct *dummy);
>  
>  
> @@ -122,8 +125,8 @@ static void kvp_timeout_func(struct work_struct *dummy)
>  	kvp_respond_to_host(NULL, HV_E_FAIL);
>  
>  	/* Transaction is finished, reset the state. */
> -	if (kvp_transaction.state > HVUTIL_READY)
> -		kvp_transaction.state = HVUTIL_READY;
> +	if (kvp_get_state() > HVUTIL_READY)
> +		kvp_set_state(HVUTIL_READY);
>  

And what if the state changed the line after this?  Oops, your code is
hosed.  See, you need a lock, do this correctly.

greg k-h